The invention relates to a yarn delivery device having a casing, a delivery drum rotatably mounted thereon, and at least one drive wheel intended to propel the delivery drum, said drive wheel having a peripheral section intended for application of a drive belt.
In known yarn delivery devices or feed mechanisms of this type (EP 0 217 373 A2), which are used in particular in numerous textile machines, the yarn delivery drum is usually propelled by means of a drive wheel which is designed in the form of a toothed belt disc or of a spur pinion, and is looped around on a portion of its circumference by a drive belt in the form of a toothed belt, which is driven from a central drive system. The toothing serves the purpose of avoiding slippage between the drive belt and the drive wheel, and in particular in the case of positive yarn supply to the textile machine, to ensure that at every point in time quantities of yarn are provided which are in a precisely defined ratio to the operating speed of the textile machine, e.g. to the rotary speed of the needle cylinder of a circular knitting machine.
When processing yarns in the form of fibre yarns, large amounts of floating fluff particles result in the atmosphere surrounding the textile machine. These among other things are caught up by the drive belt and carried along. Therefore it is conventional to provide at any point in the drive a cleaning device, in order to clean the drive belt and free it from the entrained fluff particles. Such cleaning devices for example contain two brush wheels rolling along the drive belt.
Cleaning devices of this sort have proved inadequate. Therefore, despite their use, fluff residues adhering to the drive belt are conveyed into the tooth gaps of the tooth belt discs, and in particular into the interspaces between the tooth points of the toothed belt, and are pressed into the base of the teeth of the toothed belt disc. The tooth spaces in this way are gradually and progressively filled, until their overfilling leads to a situation in which the toothed belt is pushed out of the tooth gaps, and proper propulsion is no longer possible, or the compressed fluff particles are released in an uncontrolled manner from the belt disc and drop off in the form of thick fluff clots. These are in addition frequently mixed with abrasions from the drive belt and/or the drive wheel, and mixed with oil, thereby becoming contaminated and also in addition extremely discoloured, and in particular can adopt a pitch-black colour.
As the yarn delivery devices in textile machines are frequently disposed directly above those working points at which the yarns supplied thereby are processed, there is a risk that the fluff clots will be processed together with the yarns by the textile machine. In the case of circular knitting machines, for example, the fluff clots could in this way pass into the area of influence of the knitting needles, and either destroy these or be worked into the knitted fabric to be produced by the circular knitting machine, which in this way is likewise contaminated and discoloured and thus require expensive subsequent treatment.
Corresponding problems can arise if instead of tooth belts and tooth belt discs, other propulsion means, particularly untoothed drive belts and drive rollers are used.